The Strongest Rook
by Feeruk
Summary: An alternate DxD universe in which Sona and Rias agree to accept the presence of powerful Devil at the start of their third year in Kuoh Academy to ensure their safety. How will Serafall Leviathan's Rook - none other than Naruto Uzumaki – alter the tide of events to come? AU, God-like, Hybrid Naruto. Crossover peerage.


**Disclaimer:** I do not own Naruto, Highschool DxD or any other universe that may be mentioned or brought up within this story. This is strictly a piece of fanfiction being made without any intention of ever making a profit.

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 **Author's Notes**

 **Warnings:** AU, Older, God-like, Intelligent, Mature-ish, OOC-ish Naruto. Small peerage (4-5) of various crossover characters. Harem story. Relatively heavy canon storyline. Lots of clichés. Crack-ish at times during comedic moments.

While not quite on the same level as my other Naruto/DxD crossover, Naruto will still possess God-like strength in this story and likely come across as at least moderately Gary Stu-ish. If you typically dislike fics with that sort of main character, then this isn't a story that you're likely to find enjoyable.

As I've tagged this as an AU and OOC-ish Naruto, I'm obviously using a bit of creative leeway to alter specific things about his past such as the people he has known, the abilities he has learned, the struggles he has overcome and more.

Devils who become powerful enough, regardless of whether or not they belong to another Devil's peerage, can obtain their own set of Evil Pieces within this fic. I'm not entirely caught up with the light novels yet and I'm uncertain as to whether or not that's breaking any rules that were specified within them, so I felt it wise to specify this fact ahead of time.

 **Pairings:** As noted, Naruto will have a harem within this story. He will be in a pre-existing relationship with Serafall and most of his peerage members while all others tagged will develop as the story progresses. Issei, meanwhile, will have a small harem of his own. The confirmed members of each of the aforementioned groups are as follows:

Naruto's harem: Most crossover peerage members, Serafall, Akeno, Rias, Koneko, Kuroka and Xenovia

Issei's harem: Asia, Irina, Ravel.

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 **The Strongest Rook**

 **Prologue**

* * *

 **(Sirzechs PoV)**

Anyone well-acquainted with Sirzechs Lucifer would know quite well that he was a man who was not to be trifled with. Though he had come to possess a rather wide-spread reputation for his light-hearted and oftentimes comical personality in recent history, no individual residing within the Underworld with would dare question his capability in ruling over his fellow Devils or his skill in combat. However, as the strife between the Devils, Fallen Angels and Angels had fallen to an all-time low over the past decade, it was a rather rare event to ever spot the man when he wasn't smiling or had some other expression of amusement otherwise visible within his expression.

Sitting behind the large desk of his study within his private manor, it was quite clear that the present moment was one of those rare events. Clad in a red and black suit in lieu of the formal mantle he often wore in public, the redhead's brow was deeply furrowed as he warred against his own thoughts. Elbows propped up on his desk with his interlaced fingers forming a makeshift bridge to rest his chin upon as his eyes stared blankly ahead of him, it was obvious that whatever those thoughts were had his full attention.

 _Knock Knock Knock_

Jolting upwards slightly at the noise, the redhead wasn't even given enough time to form a coherent response before the large wooden doors to his study were pushed open.

"Lucifer-sama," a silver-haired woman with matching eyes bowed slightly as she entered the room, though the gesture was so slight that the maid headband strapped onto her scalp didn't even waver from the motion. "The girls you have requested the presence of are outside."

"Thank you, Grayfia; I was just thinking on that matter. Please send them both in and then keep our other guest company if you would be so kind. I'll call for you when I would like him sent in."

"As you wish." Giving another small bow, Grayfia turned and walked out of the door before silently signaling two teenage girls that had been off to the side to step inside. As the duo entered the room, she made a simple pulling gesture in the air with her hands – small, red-colored circles appearing within her palms as she did so – before the doors slid shut with nary a sound.

"Lucifer-sama," the first girl greeted with a deep bow, her short, black hair pooling around her head even as the glasses she wore nearly slipped off of her nose before she brought a hand up to push them back into place.

"Onii-sama," the second greeted with a far less formal bow, her long, red hair falling from behind her ears only briefly before she let herself stand straight again and idly brushed them back with her hand.

"Sona, Rias," Sirzechs acknowledged them before he gestured to the two elegantly cushioned chairs in front of his desk. "Please take a seat, there is a matter that we need to discuss."

Both of them quickly did as they were bid, but it was clear from the brief glance they shot one another that they were rather confused as to what was going on. Despite his urge to ease their discomfort, the Crimson Satan momentarily found himself at a loss for words, having to take the next minute or so to think about how best to phrase what he needed to say.

"I suppose I will get right to the heart of the matter at hand rather than beating around the bush," he stated mere moments after his mind had come to the decision to simply be blunt. "I have received word of Fallen Angel activity near Kuoh Academy."

"…Fallen Angels near Kuoh?" Sona inquired, her brow furrowing slightly. "Why would they be there? They must know that it falls under my family's jurisdiction, it's incredibly reckless of them."

"That particular detail is unknown, unfortunately. I'm unaware of their motives, their numbers and even who's commanding them. The only intel we have is that they are a rogue group operating in that general location. Still, even knowing just that much, we're currently presented with a rather large problem given where you two are planning to travel next week."

Sona quickly took in a sharp breath of air, Rias mimicking the action seconds later as her mind came to the same conclusion.

"You're worried they may be after us?"

"It is as valid a theory as any, unfortunately," Sirzechs addressed his sister. "While we don't know the ultimate goal they would have for doing such a thing, it wouldn't be a far stretch for them to believe that kidnapping you two would enable them to ask nearly anything of us in return for your safe return. On the opposite end of that spectrum, if they were simply aiming to cripple our faction as a whole or obtain some manner of revenge for past wrongs, they could simply kill you both in order to deprive us of two powerful children and any hope of extending our families through either of you. There are also several other theories of an even darker nature which are even more concerning that you two can think of on your own, I'm sure."

A silence overtook the room, the faces of the two teens slowly paling at the ideas that quickly sprung up within their minds.

"Are…are we not returning to Kuoh, then?"

Rias suddenly stiffened, her head snapping towards her friend upon hearing her question before shooting back over to her brother.

"No! Onii-sama, you can't jus—"

"Calm yourself, Rias," Sirzechs spoke up calmly, waving a hand in a placating gesture. "The idea to forbid you two from going back to school until this matter is resolved was proposed by Ajuka and Falbium, but it was ultimately shot down in favor of an idea that Serafall and I came up with."

"…And what idea was that, exactly?"

 _'She really has become quite suspicious of anything I do for her as of late,'_ eyes softening slightly as his gaze remained locked onto his sister's own, he blew out a harsh-sounding breath through his nose. _'I'm one of the most influential beings in the world and yet my hands are tied from helping her get out of something as trivial as a ridiculous marriage contract. …I suppose I can't blame her for being cautious about what I do for her if I can't even fix something so simple.'_

"I know how much you enjoy your time in Kuoh, Rias, and Serafall seems to be of the opinion that Sona here enjoys her time there every bit as much as you do." Letting his gaze drift over and catch the eyes of the Sitri girl, he felt the corner of his mouth tug upwards ever so slightly upon seeing how genuinely surprised she seemed to be at that tidbit of information. "However, while we may wish for you both to continue your education there for as long as you desire, your safety is unquestionably paramount. If you both wish to continue attending the academy, in order to maintain your safety, you will have to agree to a guard accompanying you there. Furthermore, you would both also have to agree to him posing as a student within Kuoh so that he may ensure your continued protection in case the rogue Fallen Angels should make a move to try and capture you."

Another silence fell over the trio as that information was digested, both young Devils looking towards one another after several moments had passed and seemingly having some manner of silent conversation among themselves.

"I presume that we simply will not be allowed to leave if we do not accept the terms?"

"Correct. I'm afraid that anything less than the measures I have presented you with would pose too much of a risk to your safety to allow."

"I see," Sona trailed off, a sharp breath leaving her as her shoulders slumped slightly. "Who is the guard you are planning to send, if I may be so bold as to ask?"

"Ah, I'm glad you brought that up that matter!" Sirzechs chirped, the serious tone he had been addressing them with seemingly having disappeared in lieu for a much more light-hearted one. Using his left thumb, he brushed over his wedding band, silently channeling a small quantity of magic into it as he did so. Feeling a small pulse a moment later, his lips quickly pulled back into a small smile that caught both of the teens in front of him somewhat off-guard. "Grayfia should be letting him in momentarily."

As if on cue, the doors to his office slowly slid open again. As the trio turned in that direction, they could see Grayfia standing in the middle of the doorway briefly before moving slightly to the side to reveal the form of the taller man who had been standing behind her. After he stepped inside, the silver-haired maid wordlessly left the room and closed the doors once more.

The man who was now in the room with them was a fair-skinned, spiky-haired blond with three whiskers on each of his cheeks and a pair of cerulean blue eyes that were lazily drifting over the room and the inhabitants within it. Clad in a long-sleeved orange t-shirt, a pair of loose-fitting black pants that sagged noticeably around his crotch and a pair of high-top black boots with a black cat perched atop his right shoulder, he almost looked to be underdressed and acting far too casual given the high status of the individuals he was around. Despite that, however, he calmly strode into the room with his hands stuffed into his pockets and a small smile etched across his lips.

 _Smack!_

"Of course it would be him of all people…" Sona muttered, her palm now concealing the upper-half of her face from view.

"Good to see you too, So-tan~," the blond drew out teasingly as he stopped a fair distance away to remain outside of everyone's personal space. "Come on, can't you at least be a _little_ happy to hear that I'm coming to school with you?"

 _Meow_

"Yeah, what she said!" The blond continued, jerking his head towards the golden-eyed cat on his shoulder who had made the noise.

 _'Heh, a part of me truly hopes that you'll really never change, my friend.'_

"Rias," Sirzechs began, bringing everyone's attention back to him. "I know you've likely seen or heard of him at least in passing given how long you've known Sona, but I'd like to formally introduce you to Naruto Uzumaki – Serafall's Rook."

"I-it's an honor to make your acquaintance, Uzumaki-sama," the redhead girl turned and bowed low.

"Ahaha, there's no need to be so formal," Naruto began, raising his right hand – an appendage that was wrapped up in a series of white bandages – and waving it in front of his face in a nonchalant manner. "Just Naruto is fine. I'm actually quite glad to finally get to meet one of So-tan's friends, so the feeling is mutual."

"My name is _Sona_."

"I know, that's what I said," the blond shot back, turning to face her with a cheeky grin.

Face turning red from either embarrassment or anger, the Sitri heiress merely crossed her arms over her chest and quickly turned away from her sister's Evil Piece.

 _Meow_

"Shh!" Naruto suddenly claimed, raising a finger up and holding it to the cat's mouth. "We don't want to make her _too_ mad at us just yet. We've got to save some of our material for the school."

 _'I still **really** want to know how the two of them communicate like that.' _

"Speaking of which…" Sirzechs trailed off with a cough, leaving the thought unspoken. "We were just coming to the end of our little chat regarding their opinions on that very matter." Letting his gaze wander over to the Sitri heiress, he merely stared at her silently, though not without taking a bit of delight in seeing the usually stoic girl with an embarrassed blush and a slightly frustrated expression.

"…No one else would be acceptable to guard us, I presume?" Sona sighed.

"No one that would fit all of the requirements we have for the position, I'm afraid."

"Then I suppose I don't have any real choice if I wish to continue gathering possible candidates for the last piece of my peerage."

"Oh come on, don't make it seem so horrible to have me around!" Naruto claimed, patting her shoulder as he did so. "If it wasn't for that show of hers, it could've been your sister that went with you instead, you know?"

Sona's body immediately went frigid for a moment, gave a fierce-looking shake and then slowly began relaxing again.

"I accept his presence, Lucifer-sama," she claimed, hesitation no longer present in her voice.

"Good," Sirzechs chuckled. Slowly, his gaze turned towards his sister. "And you, Rias?"

"I have no qualms with him if it means I'll still be able to attend the academy."

"See? Rias doesn't even know how amazing I am yet and _she's_ fine with me being there."

Unspotted by anyone but her brother at that moment, Rias' body perked up slightly at that as her eyes grew a bit wider upon hearing how she was addressed.

"I've accepted your presence at the one place where I can have peace and solitude. Please do not push your luck much further than that, Nii-san."

 _'Oh~? I wonder when he finally got her to start calling him that.'_

"Alright, alright," the blond chortled. "I'll stop for a while."

"Thank you," Sona sighed with relief.

"Well then, now that we've settled that matter, you girls are free to leave. Naruto here will meet up with both of you shortly before you depart for Earth."

"Understood."

"Understood, Onii-sama."

Standing up and bowing, both teens promptly proceeded to exit the large room and left the two men and cat alone.

"So, what do you think?"

"She's definitely strong, but without some clever trick up her sleeve, I don't think there's any chance she'll beat the Phenex brat." Quickly reaching over and grabbing one of the now-empty chairs, Naruto quickly plopped down into it. Upon taking his new position, the cat upon his shoulder quickly hopped down into his lap and he idly began stroking a spot in between her ears. "Then again, I've never really been all that good at sensing if someone's hiding energy or something. Yoruichi, what do you think?"

"Mmm, I think you were spot on with your assessment," the cat spoke in a deep, masculine-sounding voice. "Without some sort of ace up her sleeve, there's little chance that she'll walk away from a Rating Game against him as the victor."

"An ace that the two of you could help create."

"Possibly. As I've told you in the past, I make no promises on training anyone. Fellow Nekomata or not, I don't train people I don't trust," Yoruichi declared, idly leaning back into the fingers scratching between her ears at that moment.

"Same for me," Naruto chimed in. "The things we know are far too dangerous in the hands of people who would abuse them. I'll only agree to train her once I get to know her a bit better and decide whether or not she's trustworthy."

"I have had first-hand interactions with little Koneko quite a few times already. I have very, _very_ little doubt that trusting her will be an issue for the two of you given enough time," Sirzechs smiled. "So, hypothetically speaking, do you think it would be possible for my sister to win if you two helped train her Rook?"

"It isn't an impossible outcome – just one that is highly unlikely. Unless she can learn Senjutsu as quickly as this idiot consumes ramen, there likely won't be enough time to teach her what she would need to defeat someone of the Phenex clan."

"Agreed," the blond hummed out as he continued stroking his companion's ears absentmindedly, paying no mind to the playful insult that had been shot at him. "Unless she can get a good grasp on it incredibly quickly, there's little chance that she could end up being what your sister needs to win. …Well, Sealing could work too, I suppose, but the odds of her being gifted at the latter are far less than the former."

 _'Thankfully so. The last thing we need is for more people to be skilled at Sealing of all things.'_ Shivering slightly at the very thought of a group of people mastering that particular branch of ancient and powerful Magic, the Crimson Satan quickly pushed it from his mind.

"So there is nearly no hope? Surely there must be something you can do?" Glancing from the blond's eyes down to Yoruichi's and then back again, he made no attempt to hide the slight desperation he felt.

"Relax, we have a few ideas that should make her peerage able to at least put up a good fight. We'll do everything we can to help her out," Naruto chuckled, a mischievous smile slowly pulling at his lips. "Even if she ends up losing this challenge that you're going to end up giving her though, we can always go with the back-up plan."

"…As much as I appreciate that particular offer, I have little doubt that Rias wouldn't exactly appreciate _that_ situation any more than her current one. I would like to avoid it if such a thing is at all possible."

"Yeah, yeah, I get it; just reminding you that the option is still on the table." Leaning back in the chair, the blond draped one of his arms over the back of it even while the other continued scratching the ears of his companion as she purred in content. "You know that it would only be a temporary thing until we could think of something to change her position."

 _'Temporary or not, it's still something that's a last resort.'_ Shaking his head slightly from side to side, Sirzechs felt his lips twitch upwards for a moment before a sudden shiver ran through his body. _'_ _I don't even want to imagine what Serafall's reaction to something like that would be.'_

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 **End**

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 **Post Notes**

I had the urge to write a Naruto and DxD crossover without the Sekirei involved from my other published fic in this category, so here we are. I really wanted to include a few crossover characters for various reasons, so that's why they're going to be a thing.

The ages of Devils have always confused me, so I'm going to purposely keep them rather vague.

The next chapter will have Naruto being introduced to Rias' peerage as the lot of them travel to Earth and also reveal a bit of his backstory.

As usual, no promises on updates in any kind of timely manner.


End file.
